Lung Volumes and Capacities · Physiology

Which of the following describes the state of the respiratory system when the lung volume is at Functional Residual Capacity (FRC)?

  1. Alveolar pressure reaches its most negative possible value
  2. Lung inward recoil balances outward chest wall recoil
  3. The abdominal muscles actively contract to hold the volume
  4. The lungs have reached their minimum possible volume
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Correct answer: Lung inward recoil balances outward chest wall recoil

At FRC, which occurs at the end of a quiet expiration, the inward elastic recoil of the lungs and the outward elastic recoil of the chest wall are equal and opposite. This balance point establishes the resting equilibrium volume of the respiratory system.

Difficulty: Medium Question 22 of 40

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